In the neighbouring province of Narathiwat, police officer Suriya Malaimal was shot more than 10 times as he approached his motorcycle parked at a crowded market, a police spokesman said.
Muslims make up 90 per cent of population in four southernmost Thai provinces: Yala, Pattani, Narathiwat and Songkhla
Region was semi-autonomous Islamic Malay sultanate annexed by Thailand in 1902
Several violent uprisings over the century
Muslims complain assimilation policies have restricted Malay customs
Tough approach by former PM Thaksin Shinawatra dimmed hopes of resolution
Government imposed martial law in 2004
Near daily attacks blamed on Muslim fighters have left about 2,200 people dead, including many Muslims
Lieutenant Banlae Chuvet said six gunmen were involved in the attack.
"Initial investigations show he was killed by Muslim insurgents," Banlae said.
He added that that the attackers stole the officer's gun.
Elsewhere in the south, a roadside bomb exploded, injuring two policemen.
The police had been deployed to protect teachers as they travelled to a school in Yala province, officials said, adding that the blast was triggered by mobile phone.
Teachers, like schools, have been frequent targets of attacks in Thailand's south.
An uprising in Thailand's southern Muslim-majority provinces has left about 2,200 dead since it flared in 2004.
In a separate development on Friday, Thai railway officials resumed services to southern Thailand, four days after suspected insurgents sabotaged tracks causing a train to derail in Pattani province.
About half the usual number of passengers used trains in Pattani and nearby Yala and Narathiwat provinces, despite an increased police and army presence at stations and junctions along the tracks, said Thanongsak Phongprasert, the railway's southern office director.
Train services in the three southernmost provinces were suspended on Monday after the line in Pattani was sabotaged, derailing a train and wounding nine of the train's hundreds of passengers.